1. Field of the Invention
The invention relates to a lens unit, a LED head, an exposing unit, an image forming apparatus, and a scanning apparatus.
2. Description of Related Art
A conventional lens unit is used in electrophotographic image forming apparatus having an LED head in which a plurality of LED elements (light emitting diodes) are arranged in an array or is used in a scanning apparatus (such as a scanner or a facsimile machine) having a light receiving portion in which a plurality of light receiving elements are arranged in an array. The lens unit serves as an optical system that forms, on an imaging plane, an erect one-to-one magnification image of an object in the form of a line.
Japanese Patent Application Laid-Open No. 2000-221445 (see Paragraphs 0017 to 0023 and FIG. 2) discloses a lens unit as an optical system. The lens unit includes plural lens pairs, each of which includes a first lens configured to form a converted reduced-size image of an object and a second lens configured to form a converted enlarged-size image of the converted reduced-size image, arranged in a substantially straight line. The lens unit thus forms an erect one-to-one magnification image of the object in the form of a line.